The objectives of the proposed research are to develop alphavirus replicon particle vaccines against inter-pandemic and potential pandemic strains of influenza virus. We propose a novel approach, using a propagation-defective, single-cycle, RNA replicon vector system, derived from an attenuated strain of Venezuelan equine encephalitis (VEE) virus, to produce virus-like replicon particles (VRP) expressing the hemagglutinin (HA) and neuraminidase (NA) genes of influenza A. Preliminary studies have demonstrated the safety and feasibility of this approach. The project will include six specific aims. (1) Construct and characterize VRP vaccines expressing influenza genes. (2) Perform scale-up development of processes for GMP-compliant manufacture of a bivalent influenza HA/NA VRP vaccine. (3) Perform GMP manufacture of this vaccine. (4) Perform benchmark preclinical studies and prepare a Clinical Trial Exemption (CTX) application. (5) Conduct a phase I dose-escalation clinical trial to identify an optimal human dose. (6) Conduct a phase II clinical trial in which volunteers immunized with the VRP vaccine or placebo are challenged with live influenza virus to evaluate vaccine efficacy. Vaccine construction, characterization, process scale-up, GMP manufacture, preclinical and phase I clinical testing will be performed based on previous experience with other VRP vaccines. Phase II clinical testing will utilize an established human influenza H3N2 challenge model. Results of these studies will provide "proof-of-concept" for the value of this technology as a basis for development of VRP vaccines against inter-pandemic and potential pandemic strains of influenza virus. [unreadable] [unreadable]